1. Field of the Invention
The present invention relates generally to a single phase induction motor, and more particularly, to a single phase induction motor having a centralized winding structure for use with a hermetic reciprocal compressor.
2. Description of the Related Art
A hermetic reciprocal compressor, as shown in FIG. 1, includes a sealed casing 10, an electronic device unit 20 formed in the sealed casing 10 to serve as a driving source, and a compression device unit 30 for compressing refrigerant with linear reciprocal movement by the driving force of the electronic device unit 20.
The electronic device unit 20 has a single-phase induction motor. The rotational driving force of the electronic device unit 20 is converted into the linear reciprocal movement of the compression device unit 30 by a crank device that has an eccentric shaft 31 and a connecting rod 32. The compression device unit 30 has a cylinder block 33 and a piston 35 that slides longitudinally within a bore of the cylinder block 33. One end of the piston 35 is connected to a connecting rod 32 such that the piston 35 is reciprocated within the bore of the cylinder block 33 in a linear direction in association with the rotational driving of the eccentric shaft 31, to thereby draw and compress the refrigerant.
The single-phase induction motor has a stator and a rotor that is rotated by the revolving magnetic field of the electric force generated between the stator and the rotor. On the stator, a main winding and a sub winding are wound around a polar axis of an electric angle 90xc2x0.
When alternating current (AC) power is supplied to the main winding and the sub winding from a power source (not shown), the sub winding, which is positioned ahead of the main winding by the electrical angle of 90xc2x0, is first subjected to the rotational force caused by the revolving magnetic field generated by the electric current. Since the current phase of the sub winding is ahead of the current phase of the main winding due to a capacitor connected in series with the sub winding, the rotor is caused to rotate at a high speed.
FIG. 2 is an exploded perspective view of the single-phase induction motor used in a conventional compressor, and FIG. 3 is a longitudinal sectional view of the single-phase induction motor of FIG. 2 being assembled, in which reference numeral 21 denotes the stator, 22 the rotor, and 23 and 24 the main winding and the sub winding, respectively.
As shown in FIGS. 2 and 3, twenty-four (24) stator slots 21a are formed along an inner circumference of the stator in a manner such that the slots 21a are spaced from each other by a predetermined distance. A plurality of rotor slots 22a are also formed in the rotor 22 at a predetermined distance from each other. The main winding 23 and the sub winding 24 are wound through the stator slots 21a, while there also is a winding or a permanent magnet (not shown) wound through or inserted into the rotor slots 22a. 
FIG. 4 illustrates an order by which the main winding 23 and the sub winding 24 are wound through the twenty-four stator slots 21a of the conventional single phase induction motor. As illustrated, the conventional single phase induction motor has the winding structure of a distributed windingxe2x80x94so called concentric winding for the main winding 23 and the sub winding 24.
In the distributed winding, the main winding 23 enters into the fourteenth slot (14th), and passes through the eleventh (11th), fifteenth (15th), tenth (10th), sixteenth (16th), ninth (9th), seventeenth (17th), eighth (8th), eighteenth (18th) and seventh (7th) slots and then re-enters into the twenty-third (23rd) slot, before passing through the second (2nd), twenty-second (22nd), third (3rd), twenty-first (21st), fourth (4th), twentieth (20th), fifth (5th), nineteenth (19th), and sixth (6th) slots, and then is drawn out. The sub winding 24 enters into the twelfth slot (12th), and passes through the first (1st), eleventh (11th), second (2nd), tenth (10th), third (3rd), ninth (9th), and fourth (4th) slots, and then re-enters into the thirteenth (13th) slot, before passing through the twenty-fourth (24th), fourteenth (14th), twenty-third (23rd), fifteenth (15th), twenty-second (22nd), sixteenth (16th), and twenty-first (21st) slots and then is drawn out.
In the conventional single phase induction motor, the main winding 23 and the sub winding 24 of the stator 21 are concentrically wound through the slots in an outward or inward direction, inevitably requiring an increased length of the coil end and subsequent cost increases and excessive use of copper.
In addition to the problem of increased length of the coil end due to the distributed winding structure of the main winding 23 and the sub winding 24, the conventional single phase induction motor also has a problem caused due to the structure in which the winding protrudes from opposing sides of the stator 21. That is, since the winding protrudes from the opposite sides of the stator 21, additional processes like forming, lacing and cleaning are required for the purpose of tidying up the winding, and as a result,productivity deteriorates due to the increased manufacturing processes and other resulting difficulties.
Further, since the main winding 23 and the sub winding 24 each protrude from opposite sides of the stator 21, the size of compressor inevitably unnecessarily increases.
The present invention overcomes the above-mentioned problems of the prior art. Accordingly, it is an object of the present invention to provide a single-phase induction motor having a shortened coil end, which is achieved by a centralized winding structure in which a main winding and a sub winding are wound through slots adjacent to each other, and is thus capable of reducing material costs and excessive use of copper.
Yet another object of the present invention is to provide a single-phase induction motor having a centralized winding structure in which the main winding and the sub winding are directly wound through slots adjacent to each other, requiring no separate processes like forming, lacing and cleaning for tidying up a protruded winding because the winding does not protrude, and is thus easy to manufacture.
Yet another object of the present invention is to provide a hermetic reciprocal compressor, which is smaller due to the compact-size of the single-phase induction motor.
The above objects are accomplished by a single-phase induction motor according to the present invention, including a stator having a plurality of slots; a rotor rotated by a magnetic field generated by an electric force between the stator and the rotor; and a main winding and a sub winding wound through the plurality of slots of the stator to form a revolving magnetic field on the rotor. The main winding and the sub winding form a centralized type of winding structure so that the main winding and the sub winding are wound in an alternate pattern via adjacent slots according to a certain rule which will be further described.
Since the main winding and the sub winding are wound through the slots of the stator in this centralized winding structure, the coil end length is greatly reduced, and as a result, the material costs and copper loss can also be reduced greatly.
Further, according to the present invention, the main winding and the sub winding, are wound through the slots of the stator, and do not protrude from opposite sides of the stator too much. Accordingly, processes like forming, lacing and cleaning to tidy up the protruded portion of the main winding and the sub winding, can be omitted, and therefore, the manufacturing process becomes simplified.
According to the preferred embodiment of the present invention, the stator has sixteen slots, and the main winding is inserted into slot (1a) of the stator, then passed consecutively through slots (2b), (4f), (3e), (5i), (6j), (8n), (7m), and then drawn out, while the sub winding is inserted into slot (2c) of the stator, then passed consecutively through slots (3d), (5h), (4g), (6k), (7l), (8o), (1p), and then drawn out.
The main winding is also inserted into slot (1a) of the stator, then passed consecutively through slots (2b), (2c), (3d), (7l), (6k), (6j), (5i), and then drawn out, while the sub winding is inserted into slot (7m) of the stator, then passed consecutively through slots (8n), (8o), (1p), (5h), (4g), (4f), (3e), and then drawn out.
Also, the main winding is inserted into slot (1a) of the stator, then passed consecutively through slots (2b), (2c), (3d), (3e), (4f), (8n), (7m), (7l), (6k), (6j) and (5i), and then drawn out, while the sub winding is inserted into slot (3e) of the stator, then passed consecutively through slots (4f), (4g), (5h), (5i), (6j), (2b), (1a), (1p), (8o), (8n), (7m) and then drawn out.
In order to generate a magnetic field from the electric force of the stator, a winding or a permanent magnet can be wound into, or inserted into the plurality of slots of the rotor that penetrate through the rotor.
The rotor can have skews formed at a pitch identical to a pitch of the slots of the stator, for reducing harmonic waves, noise and vibration. Each skew of the rotor is in the shape of the alphabet symbols xe2x80x98Ixe2x80x99 or xe2x80x98Vxe2x80x99.
Meanwhile, another object of the present invention can be achieved by a hermetic reciprocal compressor according to the present invention, which utilizes the single-phase induction motor as described above. Since the main winding and the sub winding do not protrude from the opposite sides of the stator too much, the size of the compressor can be reduced.